Direct steel-making process

Abstract

Steel sheet is formed directly from iron ore concentrate by reducing a bed of iron ore concentrate, particularly high purity magnetized magnetic gamma hematite, to a low density hot cake of carburized metallic iron and then hot rolling the hot cake to a metallic sheet of full density (meeting market specification).

What I claim is: 
     
       1. A method of making steel, which comprises: forming a gas-permeable bed of particulate iron ore or concentrate,   passing a reducing gas through said particulate iron ore or concentrate to form a coherent porous hot cake of metallic iron in which sintered metal particles are fused to one another, and   compacting the hot cake to a metal sheet.   
     
     
       2. A method of making steel, which comprises: reducing a bed of particulate iron ore or concentrate to a hot cake of metallic iron, said iron ore being magnetic gamma hematite containing less than about 0.5 wt % impurities, and   compacting the hot cake to a metal sheet.   
     
     
       3. The method of claim 2 wherein said magnetic gamma hematite is magnetized. 
     
     
       4. A method of making steel, which comprises: reducing a bed of particulate ore or concentrate to a hot cake of metallic iron, said bed of particulate iron ore having a bulk density of about 150 to about 250 pounds per cubic foot and is composed of particles of iron ore concentrate sized minus 50 mesh and plus 200 mesh, and   compacting the hot cake to a metal sheet.   
     
     
       5. The method of claim 4 wherein sad bed of particulate iron ore is reduced by passing a reducing gas stream comprising a mixture of carbon monoxide and hydrogen through said bed of iron ore at a temperature at least sufficient to effect said reduction but not sufficient to melt the iron. 
     
     
       6. The method of claim 5 wherein said reducing gas stream comprises a mixture of carbon monoxide and hydrogen having a ratio of 2 CO:H 2  to 3 CO:H 2 . 
     
     
       7. The method of claim 6 wherein said reduction is effected at a temperature of about 1150° to about 1300° C. 
     
     
       8. The method of claim 7 wherein said temperature is about 1200° C. 
     
     
       9. The method of claim wherein said hot cake is exposed to a carbon gas atmosphere for a sufficient time to provide a desired level of carburizing of metal in said cake prior to said compacting step. 
     
     
       10. The method of claim 9 wherein said carbon gas atmosphere is provided by a mixture of carbon monoxide and carbon dioxide. 
     
     
       11. A method of making steel, which comprises: reducing a bed of particulate iron ore or concentrate to a hot cake of metallic iron, and   compacting the hot cake in such manner as to expel gases from said cake and to provide a metal sheet having a full density of about 7.8 g/cc.   
     
     
       12. The method of claim 11 wherein said compaction is effected by feeding said cake through a nip between counter-rotating rollers at a linear speed corresponding to the rotational speed of the rollers. 
     
     
       13. The method of claim 12 wherein said cake is hot rolled to a thickness of no greater than about 15% of the cake thickness. 
     
     
       14. The method of claim 12 wherein said cake is hot rolled to a length corresponding to an elongation of at least about 50% of the length of the cake.